1. Field of Endeavor
The invention relates to an apparatus for inspection of a narrow air gap between two surfaces with a probe, wherein at least one of the two surfaces is ferromagnetic. The invention relates in particular to an apparatus having a motor for movement of the probe, wherein the motor is arranged outside the gap and the probe can be moved into the gap through a single access.
2. Brief Description of the Related Art
Machines, motors and industrial apparatuses with a long operating life are typically inspected for their serviceability at regular time intervals. For example, turbines, boilers or generators are inspected for damage on the surfaces of the components, in order to prevent failure or damage during operation, in that any damage must be rectified or components must be replaced. In order to carry out an inspection with as little effort as possible and in a short time, the machine should, if possible, not be disassembled. However, only a limited amount of space and narrow accesses are frequently available for inspection. For example, the stator and rotor of the generator are inspected via a narrow air gap between the surfaces of the stator and rotor.
Various inspection apparatuses are known, as follows, for inspections of this type.
By way of example, U.S. Pat. No. 6,672,413 discloses a remotely controlled apparatus for inspection of spaces which are not accessible by people. This includes one or more carriages which are connected to one another by a hinge. The carriages have a motor as well as magnets which ensure contact with the surfaces, in particular with surfaces from which the apparatus would otherwise slide off because of the force of gravity. Because of its size and complexity, the apparatus is suitable only for spaces above a specific size.
EP 684483 discloses a system for inspection of a generator whose rotor need not be removed for inspection. It includes one or more sensors on a carriage with wheels which roll at the same time along the surfaces of the rotor and in slots in the stator. The apparatus is moved by a motor outside the machine to be inspected and a cable which extends over the length of the machine to its two ends. While the system allows inspection of a narrow gap with a size of more than 40 mm, access is required from both sides of the machine for its installation.
EP 1420260 discloses a detector for inspection of a generator stator with a built-in rotor having a rail which is mounted at one end of the stator and is magnetically attached in stator slots. After installation of the rail, the carriage can be moved along the rail by a remotely controlled drive, a cable which can be pulled on, preferably with a direction-changing roller, and a spring.
EP 1233278 discloses an apparatus for inspection of the air gap between the stator and the rotor of a generator with a built-in rotor, for whose attachment access is required from both sides of the air gap.
U.S. Pat. No. 6,100,711 discloses an apparatus for inspection of an air gap in a generator. The apparatus includes a telescopic mast which is brought into contact with its side walls by side elements for positioning in the air gap. A motor for onward movement of the apparatus is mounted on this. The apparatus requires a minimum air gap height of half an inch.
EP 1 863 153 discloses an inspection apparatus for an air gap which includes a mast in the form of an expandable tube which can be folded up and on which a sensor head is mounted. For this purpose, the mast includes two parts which are separated from one another along their length and thus widen the mast. The mast is composed of material which can be rolled up and can be rolled out and rolled up by a drive outside the air gap. The mast is inserted, in a folded-up state, into the air gap from one end of the gap. Once it has been inserted, its width is widened, as a result of which it achieves the required stiffness to move the sensor onward. The sensor and mast are then guided by the drive along the length of the gap. When the sensor is not in use, the mast is stored, rolled up, in its folded-up state.